There are times when it may be desirable for intake and exhaust valves of an internal combustion engine to open less than the full stroke driven by the camshaft. This affects engine performance as a function of speed and may improve fuel efficiency and reduce emissions. With a smaller valve opening less air or fuel-air mixture may be drawn into the cylinder and/or exhaust may be discharged less rapidly. The timing of the intake and the exhaust valves of a cylinder may also be regulated so that there is little, if any, overlap when both valves are partly open.
The present invention relates to internal combustion engines with rocker arms for operating the valves. The rocker arms are pivoted by pushrods engaging a rotating camshaft and the rocker arms open valves to the engine cylinders. In such arrangements, a valve opens a certain distance in direct proportion to the eccentricity of the cam or stroke of a pushrod.
In an engine employing this invention, the cam remains the same and the stroke of the pushrod remains the same. Means are provided, however, for reducing the stroke of the valve relative to the stroke of the pushrod. Broadly, this is accomplished by permitting the rocker arm pivot to move.